Many dyes used in printing designs on carpet must be chemically fixed to the carpet fibers before the printed product may be packaged and shipped. Although existing commercial dyestuffs may be fixed at room temperature, such fixing requires a period on the order of twenty-four hours and is much too long for a production environment. Consequently, manufacturers of printed carpet utilize devices such as atmospheric steamers to heat the dyed carpet and accelerate fixing. One such steamer used in fixing dye on carpet tiles promotes more rapid fixing by conveying each tile through a cloud of atmospheric-pressure steam for approximately four and one-half minutes.
While atmospheric steamers substantially increase the quantity of printed carpet or carpet tiles which may be produced in a given period of time, such steamers are not without limitations. Because existing steamers subject carpet tiles to an environment maintained at 212.degree. F. for several minutes, some tiles curl as their backings distort because of direct exposure to the intense heat. Such steamers also are relatively large in size, typically approximately forty feet long, to ensure adequate steaming for the tiles at conventional conveyor speeds. As can readily be imagined, substantial floor space is required for these devices.
Using atmospheric steam also results in uneven fixing of dye through the depth of the carpet. Because steam is lighter than air, cooler air embedded deep in the carpet fibers is not displaced by the steam but rather remains in contact with the dyestuffs. Such dyes remain unfixed even as the carpet exits the steamer, requiring that the carpet be washed to flush the unfixed dye. After the carpet is washed it must be dried, once again subjecting the backing to a period of intense heat, before it may be packaged and shipped.
Several systems exist for treating various materials with pressurized rather than atmospheric steam. U.S. Pat. Nos. 2,621,504 and 2,008,230 to Spooner and 3,868,215 to Frezza, for example, disclose closed systems for steaming textiles in which high velocity steam is projected onto the textiles. Even if such systems could be used for accelerating dye fixing, the mere presence of the printed material in the closed chamber for any length of time might cause the backing temperature to rise to unacceptable levels. Further, high velocity steam impinging on materials such as carpet fibers likely would cause some fibers to contact adjacent fibers. If the adjacent fibers are printed with a different color dye, crocking, or dye transfer from one colored fiber to another, may result.